Complementary metal-oxide-semiconductor (CMOS) technology is widely used in microprocessors, microcontrollers, static RAM, and other circuits that employ digital logic circuits. CMOS digital logic offers relatively high speed, low power dissipation, high noise margins, and will operate over a wide range of input voltages.
CMOS digital logic circuits use a combination of p-type metal-oxide-semiconductor field-effect transistors (PMOSFET or PMOS for short) and n-type metal-oxide-semiconductor field-effect transistors (NMOSFET or NMOS for short). The “metal” part of the name is a bit misleading. Although some MOSFETs use metal as gates, many modern MOSFETs use polysilicon to form gates.
The PMOS transistor creates low resistance path between its source and drain contacts when a low gate voltage is applied, and high resistance when a high gate voltage is applied. On the other hand, the NMOS transistor creates high resistance path between source and drain when a low gate voltage is applied, and low resistance when a high gate voltage is applied.
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